As a method for realizing reduced bit cost of a nonvolatile semiconductor memory device and also enhancing memory performance thereof, scaling down of a memory cell is promising. However, scaling down of the memory cell has become technically difficult.
It has thus been proposed to use organic molecules for a charge trapping layer. Because various organic molecules can be formed by organically synthesize a variety of molecular structures and substituent groups, desired electrochemical properties can be applied to the organic molecules. And structural unit of the organic molecules is small. Therefore, the organic molecules may realize further scaling-down of the memory cell. When the organic molecules are used for the charge trapping layer, a monolayer is often applied because of its film uniformity and small thickness. In particular, organic molecules that form the monolayer in a self-assembling manner are often selected.
However, the surface of the organic molecular film often has hydrophobic (lipophilic) properties. For example, even when it is attempted to form an oxide film on this organic molecular film by Atomic Layer Deposition (ALD), an oxide film with inferior film quality is formed due to lack of hydroxyl groups that serve as reactivity sources in ALD. The oxide film with inferior film quality has a large leakage current and a low break down voltage. This thus brings about problems of degradation in data retention time for the memory cell and degradation in reliability.